The post-Copenhagen climate negotiations seem to be diverging, at least on the question of targets. Brackets, denoting disagreement, have if anything proliferated in the draft texts. The latest from Bonn:
AD HOC WORKING GROUP ON LONG-TERM COOPERATIVE ACTION UNDER THE CONVENTION
Eleventh session Bonn, 2–6 August 2010
Item 3 of the provisional agenda Preparation of an outcome to be presented to the Conference of the Parties for adoption at its sixteenth session to enable full, effective and sustained implementation of the Convention through long-term cooperative action now, up to and beyond 2012
Text to facilitate negotiations among Parties
4. Parties should collectively reduce global emissions by  per cent from 1990 levels by 2050 and should ensure that global emissions continue to decline thereafter. Developed country Parties as a group should reduce their greenhouse gas emissions by [[75-85][at least 80-95][more than 95] per cent from 1990 levels by 2050] [more than 100 per cent from 1990 levels by 2040].
18. These commitments are made with a view to reducing the aggregate greenhouse gas emissions of developed country Parties by [at least] [25–40] [in the order of 30]    [X* per cent from  [or 2005] levels by  [and by [at least] [YY] per cent by 2050 from the  [ZZ] level].
Hat tip: Travis Franck.
Today, Drew Jones and I presented a simple model as part of the TÃ¤llberg Forum’s Washington Conversation, ‘The climate deal we need.’ Our goal was to build from some simple points about the bathtub dynamics of the carbon cycle and climate to yield some insights about what’s needed. Our aspirational list of insights to get across included,
- stabilizing emissions near current levels fails to stabilize atmospheric concentrations any time soon (because emissions now exceed uptake of carbon; stabilization continues that condition, and the residual accumulates in the atmosphere)
- achieving stabilization of atmospheric CO2 at low levels (Hansen et al.’s 350 ppm) requires very aggressive cuts (for the same reason; if carbon cycle feedbacks from temperature kick in, negative emissions could be needed)
- current policies are not on track to meaningful reductions (duh)
- nevertheless, there is a path (Hansen et al.’s “where should humanity aim” paper lays out one option, and there are others)
- starting soon is essential (the bathtub continues to fill while we delay – a costly gamble)
- international negotiation dynamics are tricky due to diversity of interests, coupled problem spaces, and difficulty of transfers (simulations shadow this)
- but everyone has to be on board or little happens (any one major region or sector, uncontrolled, can blow the deal by emitting above natural uptake)
A good moment came when someone asked, “Why should we care about staying below some temperature threshold?” (I think a scenario with about 3.5C was on the screen at the time). Jim Hansen answered, “because that would be a different planet.”
The conversation didn’t lead to specification of “the deal we need” but it explored a number of interesting facets, which I’ll relate in a few follow-on posts.